1. Field of the Invention
The present invention relates to a test apparatus used for semiconductor chip packages and, more particularly, to a burn-in test apparatus used for ball grid array (BGA) packages.
2. Description of the Related Art
Semiconductor chip packages containing integrated circuit chips may have defects which appear some time after fabrication or assembly. Many such defective packages break down within approximately one thousand hours after use. For this reason, semiconductor chip packages are often subjected to a burn-in test before sale. In the burn-in test, the packages undergo extreme electrical and thermal stress for a period of time at an elevated temperature. For example, the burn-in test for some packages utilizes a temperature of about 80 to 125° C. in order to apply thermal stress to the packages.
Recently, the use of Ball Grid Array (BGA) packages has increased. For BGA packages, the burn-in test often requires an ultrahigh temperature of about 125° C. or more in order to guarantee the ultimate reliability of the products.
FIG. 1 shows, in a cross-sectional view, a prior an burn-in test apparatus 300 used for the BGA packages. A test socket 310 of the prior an burn-in test apparatus is shown in FIG. 1. FIGS. 2 and 3 show, a side view and a sectional view, respectively, of test socket 310.
The burn-in test apparatus 300 is a known type of burn-in tester (MBT) that creates the required temperature conditions by using heated air. The apparatus 300 includes a burn-in chamber 350, a heating unit 370, an air supply duct 380, and an exhaust duct 410.
The burn-in chamber 350 provides a space where suitable test operations can be performed on BGA packages 310. The burn-in chamber 350 has a temperature sensor 355 to measure the internal temperature of the chamber 350. The BGA packages 310 are held in test sockets 310 that are positioned on the burn-in board 330. A number of burn-in boards 330 are positioned in a rack 345. The rack 345 has guide rails 346 that allow easy loading and unloading of the burn-in boards 330. The rack 345 also establishes connections between the packages 310 and a test system unit (not shown).
As shown in FIGS. 2 and 3, the test socket 310 is composed of a socket body 311, a plurality of contact pins 313, a holder 315, and a cover 321. The BGA package 10 is inserted into the socket body 311 and fixed in position by the holder 315. The holder 315 is moved into position by operation of the cover 321. A male guide 323 extends downward from one side of the cover 321. The guide 323 moves up and down in a female guide 316 that is recessed in one side of the socket body 311. The cover 321 is opened and shut in a vertical direction. The solder balls 15 that are located on the bottom face of the BGA package 10 are electrically coupled to the contact pins 313 that are located in the socket body 311.
The heating unit 370 is positioned above the burn-in chamber 350 and it heats the air. The heating unit 370 includes a heater 371, and an air blower 373. The blower 373 produces a current of heated air from the heating unit 370 to the air supply duct 380. The heating unit 370 has at least one air intake 375 through which non-heated air flows from the outside into the heating unit 370.
The air supply duct 380 is positioned at one side of the burn-in chamber 350 and provides a passage through which heated air flows from the heating unit 370 into the burn-in chamber 350. The exhaust duct 410 is positioned at the other side of the burn-in chamber 350 and provides a passage through which heated air flows from the burn-in chamber 350 to the outside. The exhaust duct 410 has an exhaust port 415 to allow heated air to flow to the outside. A perforated plate 381 with holes 383 is located at the interface between the burn-in chamber 350 and the air supply duct 380. Similarly, another perforated plate 411 with holes 413 is located at the interface between the burn-in chamber 350 and the exhaust duct 410.
At the beginning of the burn-in test, the heater 371 heats air supplied from the outside through the air intake 375. The air blower 373 supplies heated air to the burn-in chamber 350 through the air supply duct 380 and the perforated plate 381. When the temperature measured by the sensor 355 reaches a given value, the heater 371 stops heating. If the temperature inside the chamber 350 exceeds a given value, air inside the chamber 350 is exhausted to the outside through the exhaust duct 410. On the other hand, if the temperature is below a given value, the heater 371 is again operated.
The above-discussed conventional burn-in test apparatus 300 has the following drawbacks. When the burn-in chamber 350 is crowded, the space between the adjacent upper and lower burn-in boards 330 is so narrow that heated air cannot flow easily. It is therefore difficult to reliably control the temperature of the BGA package 10 contained in each test socket 310. Also, the BGA package 10 generates heat during burn-in tests, and such heat may stay in the narrow space between the burn-in boards 330 and not be quickly exhausted.
The air flow may be hampered by the structure of the test socket 310. There is no space that permits significant air flow between the solder balls 15 and the contact pins 313. Thus, the temperature inside the test socket 310 may exceed the melting point of solder, and this may lead to melting of the solder balls 15. This may become a serious issue for advanced, highly-integrated and smaller packages. In addition, the ball-melting problem may give rise to problems with the test socket 310, increasing repair expenses and lowering productivity. The ball-melting problem may become a bottleneck in the development of new products.